Response of spinach ( Spinacea oleracea) to the added fluoride in an alkaline soil

Abstract

The influence of soil contamination by inorganic fluoride (NaF) on the uptake and accumulation of fluoride in the shoot and root of spinach ( Spinacea oleracea) was investigated in pot experiment under controlled conditions. The soluble fluoride in soil varied between 2.57 mg kg −1 soil and 16.44 mg kg −1 soil in the treatment range of 0–800 mg NaF kg −1 soil. It was found that the concentration of the total fluoride in shoot and root varied between 23.5 mg kg −1 dry wt. (control) and 219.8 mg kg −1 dry wt. (at 800 mg NaF kg −1 soil). The fluoride concentration in shoot and root showed a linear trend. At the added fluoride concentration beyond 200 mg NaF kg −1 of soil, the spinach root retained more fluoride than shoot. In the treatment range 0–800 mg NaF kg −1 soil, the water labile fluoride in the juice varied from 0.32 to 0.78 ppm in shoot and 1.03 to 2.79 ppm in the root. No visible symptom of phyto-toxicity was noticed with the treatment from 0 to 800 mg NaF kg −1 soil. It was inferred from this study that spinach ( S. oleracea) accumulates fluoride at tissues level and has a distinct mechanism of partitioning of water labile fluoride and total fluoride in the tissues.